Two-cycle internal combustion engine including means for varying cylinder port timing

ABSTRACT

The two-cycle internal combustion engine includes an engine block having a cylindrical wall defining a cylinder having a head end, a piston mounted for reciprocative movement in the cylinder, and a passage in the engine block, such as an exhaust passage, a transfer passage, or a crankcase fuel intake passage, terminating at the cylinder wall in a port, such as an exhaust port, a transfer port or a piston-controlled, crankcase fuel intake port, having upper and lower edges. A valve mounted in the passage for movement relative to the port is operable to selectively vary the effective distance of one of the port edges from the cylinder head end and thereby provide the capability of varying the timing of the port opening and/or closing as required to obtain optimum engine performance at different operating conditions.

This is a division of application Ser. No. 141,906, filed Apr. 21, 1980,now U.S. Pat. No. 4,341,188.

FIELD OF THE INVENTION

This invention relates to two-cycle internal combustion engines and,more particularly, to means for varying the timing of the opening orclosing of various ports in the engine cylinder, such as an exhaustport, a fuel intake port and a transfer port.

BACKGROUND--PRIOR ART

For optimum performance of two-cycle internal combustion engines underdifferent load or operating conditions, it is desirable to vary thetiming for opening and/or closing the exhaust, transfer or fuel intakeports depending upon the operating conditions. For instance, it isdesirable to open the exhaust port later during the expansion stroke ofthe piston for maximum power and fuel efficiency at lower engine speedsand to open the exhaust port earlier during the expansion stroke whenthe engine is operating under lower load, higher speed conditions.Variations of the timing of transfer port opening is desirable undercertain operating conditions for optimization of power and fuel economy.For two-cycle engines having a fuel intake port controlled by thepiston, early opening of the intake port is more desirable for highspeed power, whereas later opening of the intake port is more desirablefor lower speeds.

Examples of prior art constructions for varying the timing of theopening and/or closing of various ports in the cylinder a two-cycleinternal combustion engine are disclosed in the United States. StillU.S. Pat. No. 1,514,476 issued Nov. 4, 1924 and the Meulien U.S. Pat.No. 2,714,879 issued Aug. 9, 1955.

Examples of prior art constructions for two-cycle internal combustionengines including a valve in an exhaust, a fuel intake passage or, atransfer passage for controlling flow from or into the engine cylinderare disclosed in the following U.S. Patents:

    ______________________________________                                        PATENTEE   U.S. PAT. NO.  ISSUE DATE                                          ______________________________________                                        Wollery    1,101,374      June 23, 1914                                       McCabe     1,743,558      January 14, 1930                                    Ewing      1,912,574      June 6, 1933                                        Garve      2,189,106      February 6, 1940                                    Onishi     3,817,227      June 18, 1974                                       ______________________________________                                    

SUMMARY OF THE INVENTION

The invention provides a two-cycle internal combustion engine includingan engine block having a cylindrical wall defining a cylinder having ahead end, a piston mounted for reciprocative movement in the cylinder, apassage in the engine block terminating at the cylinder wall in a porthaving upper and lower edges, and valve means mounted in the passage forvarying the effective distance of one of the port edges from thecylinder head end.

The valve means can be mounted in the engine block to vary the effectivedistance of the upper edge of an exhaust port or a transfer port fromthe cylinder head end or to vary the effective distance of the loweredge of a piston-controlled fuel intake port from the cylinder head end.

In one embodiment, the valve means includes a valve member having anedge portion and mounted for radially reciprocative movement relative tothe cylinder wall and to the port between a first position when thevalve member edge portion is spaced radially outwardly from thecylindrical wall and does not substantially affect the effectivedistance of the port edge from the cylinder head end and a secondposition wherein the valve member edge portion is located adjacent thecylinder wall and the port and acts as an edge of the port toeffectively change the distance thereof from the cylinder head end.

In another embodiment, the valve means comprises a rotary valve memberincluding an elongated barrel section and an axially extending notch inthe barrel section having an edge and a length substantially coextensivewith the width of the port. The barrel section is mounted transverselyof the engine passage and adjacent to the port for rotational movementbetween a first position wherein the notch is located relative to theport so as not to substantially affect the effective distance of theport edge from the cylinder head end and a second position wherein aportion of the barrel section extends past the port edge and the notchedge effectively acts as one edge of the port.

In a further embodiment, the valve means comprises a valve memberincluding an elongated barrel section and a passageway in the barrelsection for registering with the engine port and the engine passage andhaving an inlet which has a transverse edge, side edges and a shapedifferent from that of the port. The barrel section is mountedtransversely of the passage and adjacent the port for rotationalmovement between a first position wherein the passageway inlet does notsubstantially affect the effective distance the one edge of the portfrom the cylinder head end or the effective opening area of the port anda second position wherein the transverse edge and the side edges of thepassageway inlet extend inwardly from the respective edges of the portto define a smaller opening, with the transverse edge of the passagewayinlet effectively acting as the upper or lower edge of the port.

One of the principal features of the invention is the provision of atwo-cycle internal combustion engine including a simple means forselectively varying the timing of the opening or closing of a port inthe engine cylinder, such as an exhaust port, a transfer port, or a fuelintake port, to optimize engine performance under different operatingconditions.

Another of the principal features of the invention is the provision of atwo-cycle internal combustion engine including a passage terminating atthe cylinder wall in a port having upper and lower edges and a valvemounted in the passage for movement relative to the port to vary theeffective distance of one of the port edges from the cylinder head end.

Another of the principal features of the invention is the provision ofsuch a two-cycle internal combustion engine wherein the valve isarranged to also vary the effective area of the port.

Other features and aspects of the invention will become apparent tothose skilled in the art upon reviewing the following description,drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, partially schematic, sectional view of oneembodiment of a two-cycle internal combustion engine incorporatingvarious of the features of the invention, shown with the piston nearbottom dead center.

FIG. 2 is a perspective view of the exhaust port control valve of theengine illustrated in FIG. 1.

FIG. 3 is a fragmentary, sectional view of an alternate embodiment of avalving arrangement for controlling the timing of exhaust port opening.

FIG. 4 is a perspective, partially broken view of the exhaust portcontrol valve of the embodiment illustrated in FIG. 3.

FIGS. 5 and 6 are diagrammatic representations of the effective exhaustport opening when the exhaust port control valve in the engine of FIG. 3is in the high port and low port positions, respectively.

FIG. 7 is a fragmentary, sectional view of an alternate embodiment ofthe valving arrangement for controlling the timing of exhaust portopening.

FIG. 8 is a fragmentary, perspective view of the exhaust port controlvalve in the embodiment illustrated in FIG. 7.

FIGS. 9 and 10 are diagrammatic representations of the effective exhaustport opening when the exhaust port control valve of the engineillustrated in FIG. 7 is in the high and the low port positions,respectively.

FIG. 11 is a fragmentary, sectional view of another alternate embodimentincluding a valving arrangement for controlling the timing of thetransfer port opening.

FIG. 12 is a fragmentary, sectional view of another alternate embodimentincluding a valving arrangement for controlling the timing of fuelintake port opening.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of the construction and arrangement of parts set forth inthe following general description or illustrated in the accompanyingdrawings, since the invention is capable of other embodiments and ofbeing practiced or carried out in various ways. Also, it is to beunderstood that the phraseology or terminology employed herein is forthe purpose of description and not of limitation.

GENERAL DESCRIPTION

Illustrated in FIGS. 1 and 2 is a two-cycle internal combustion engine14 including a block 15 defining a cylinder 16 having a combustionchamber 17 and a cylinder head 18 which has a threaded aperture forreceiving a spark plug 20. The engine 10 further includes a crankcase 22extending from the combustion chamber 16.

Mounted for reciprocative movement inside the cylinder 16 is a piston 24having upper and lower edges 25 and 26 and connected, via a connectingrod 27, to a crankshaft 28 extending through the crankcase 22.Reciprocative movement of the piston 24 cyclically produces relativelyhigh and low pressure conditions in the crankcase 22 in the usual mannerwith maximum and minimum crankcase pressure existing when the piston 24is at bottom dead center and top dead center, respectively.

A fuel-air mixture is introduced into the crankcase 22 in response tovariations in the crankcase pressure in any known manner. The crankcase22 is connected in communication with the combustion chamber 16 by oneor more transfer passages 30 (one shown) extending in the engine block15. Each transfer passage 30 terminates at the cylinder wall in atransfer port 32 having upper and lower edges 34 and 35 located atpredetermined distances from the head end 36 of the cylinder 16. Acharge of the fuel-air mixture, flowing from the crankcase 22 throughthe transfer passage 30, is introduced into the combustion chamber 17 asthe upper edge 25 of the piston 24 uncovers the transfer port 32 duringtravel from top dead center toward bottom dead center.

The engine block 15 also includes one or more exhaust passages 38 (oneshown), each terminating at the cylinder wall in an exhaust port 40having upper and lower edges 42 and 43 located at predetermineddistances from the cylinder head end 36. Combustion products or exhaustgases are exhausted from the combustion chamber 17 and dischargedthrough the exhaust passage 38 as the upper edge 25 of the piston 24uncovers the exhaust port 40 during travel from top dead center towardbottom dead center.

The upper edges 34 and 42 of the transfer port 34 and the exhaust port40 preferably are located relative to the cylinder head end 36 andrelative to each other to provide exhaust port opening relative totransfer port opening which produces the most efficient engineperformance at high speed, low load conditions. At lower speed, higherload conditions, later exhaust port opening relative to transfer portopening usually produces a more efficient engine performance.

Movably mounted in the exhaust passage 38 adjacent the exhaust port 40is a valving or flow adjusting arrangement arranged to vary theeffective distance of the upper edge 42 of the exhaust port 40 from thecylinder head end 36 and thereby vary the timing of the exhaust portopening relative to the transfer port opening. While various valvingarrangements can be used, in the specific construction illustrated inFIGS. 1 and 2, the valving arrangement includes a plate-like valvemember 50 having an inner end 52 including an arcuate edge portion 54which has a concave contour corresponding to that of the cylinder wall.The valve member 50 is mounted in the engine block 12 for radiallyreciprocative movement relative to the cylinder wall and to the exhaustport 40 between a first or high port position (illustrated by solidlines in FIG. 1) and a second or low port position (illustrated bydashed lines in FIG. 1).

When the valve member 50 is in the high port position, the edge portion54 is spaced radially outwardly from the exhaust port 40 and has nosubstantial effect on the distance of the upper edge 42 of the exhaustport 40 from the cylinder head end 36, and thus, no substantial effecton the timing of exhaust port opening. When the valve member 50 is inthe low port position, the edge portion 54 is located adjacent thecylinder wall and effectively acts as the upper edge of the exhaust port40. That is, the upper edge of the exhaust port 40 is effectivelylowered, resulting in the exhaust port 40 opening later as the piston 24travels toward bottom dead center.

When the valve member 50 is located at positions intermediate the highand low port positions, the edge portion 54 effectively acts as theupper edge of the exhaust port 40, at a decreasing distance from thecylinder head in 36 as the valve member 50 is moved from the low portposition toward the high port position. The edge portion 54 preferablyis chamfered as illustrated in FIGS. 1 and 2.

Means are provided for selectively moving the valve member between thehigh port and low port positions. In the specific constructionillustrated by solid lines in FIG. 1, such means includes a pivotallymounted hand lever 56 connected to the valve member 50 via a link 58having one end pivotally mounted at 60 on the hand lever 56 and theopposite end pivotally mounted at 62 on the valve member 50. Theoperator can change the timing of exhaust port opening, as required tooptimize engine performance for different operating conditions, bymoving the hand lever 56 in the appropriate direction. For example, ifthe engine is being used in a marine propulsion device for a racingboat, the driver can move the hand lever clockwise from the solidposition illustrated to effect a low exhaust port condition which ismore desirable for engine idling or prior to achieving planing of theboat when maximum power is required at low engine speeds. After the boatis planing, the driver can move the hand lever 56 counterclockwise toeffect a higher exhaust port condition, which is more desirable forhigher speed, lower load conditions.

If desired, means can be provided for automatically moving the valvemember 50 in response to a variable engine operating parameter to obtainoptimum exhaust port position for different engine operating conditions.For instance, as illustrated diagrammatically by the dashed lines inFIG. 1, such means can include a power actuator 66, such an electric orhydraulic driven reciprocative member for operating the valve member 50,and a controller 68 which receives a signal from a device 70 measuringengine speed and produces a signal for operating the power actuator 66in response to variations in engine speed.

In the alternate construction illustrated in FIGS. 3-6, the valvingarrangement for controlling the timing of exhaust port opening comprisesa rotary valve member 72 including an elongated barrel section 73 havingan axially extending notch 74 which has an edge 76 and a lengthsubstantially coextensive with the width of the exhaust port 40a. Thebarrel section 73 extends traversely of the exhaust passage 38a and ismounted in the engine block 15 adjacent the upper edge 42a of theexhaust port 40a for rotational movement between a first or high portposition and a second or low power position.

When the barrel section 33 is in the high port position (illustrateddiagrammatically in FIG. 5 and by solid lines in FIG. 3), the notch 74is situated with respect to the exhaust port 40a such that the notchedge 76 does not substantially affect the effective distance of theupper edge 42a of the exhaust port 40a from the cylinder head in 36.When the barrel section 73 is in the low port position (as illustrateddiagrammatically in FIG. 6 and by dashed lines in FIG. 3), a portion ofthe barrel section 73 extends past the upper edge 42a of the exhaustport 40a and the notch edge 76 effectively acts as a lower upper edge ofthe exhaust port 40a.

When the barrel section 73 is located at positions intermediate the highand low port positions, the notch edge 76 effectively acts as the upperedge 42a of the exhaust port 40a, at a decreasing distance from thecylinder head end 36 as the barrel section 72 is moved from the low porttoward the high port position.

At least one end of the barrel section 73 extends exteriorly of theengine block 15 and (FIG. 4) an arm 78 is mounted thereon. The barrelsection 73 is rotated between the high and low port positions bysuitable means connected to the arm, such as a hand lever or anautomatic control described above in connection with the constructionillustrated in FIGS. 1 and 2.

FIGS. 7-10 illustrate an alternate construction of a valving arrangementfrom controlling the timing of the exhaust port opening. Thisconstruction is arranged and operates in a manner similar to theembodiment illustrated in FIGS. 3-6, except the rotary barrel section 80of the valve member is arranged to also vary the effective shape of theexhaust port 40b while the effective distance of the upper edge 42b ofthe exhaust port 40b from the cylinder head end is being varied. Morespecifically, the barrel section 80 is larger than the barrel section 73in the construction illustrated in FIGS. 3-6 and entirely encompassesthe exhaust passage 38b. The barrel section 80 has a notched passageway82 in registry with the exhaust port 40b and includes a transverse edge86 and side edges 88.

When the barrel section 80 is in the first or high port position(illustrated diagrammatically in FIG. 9 and by solid lines in FIG. 70)the passageway inlet is situated with respect to the exhaust port 40bsuch that the passageway 82 does not substantially affect the effectivedistance of the upper edge 42b of the exhaust port 40b from the cylinderhead end. When the barrel section 80 is in the second or low portposition (illustrated diagrammatically in FIG. 10 and by dashed lines inFIG. 70) the transverse edge 76 of the passageway inlet is situatedinwardly from the upper edge 42b (i.e., below) of the exhaust port 40band the side walls 88 of the passageway inlet 84 are situated inwardlyfrom the exhaust port sidewalls 90.

Thus, the transverse edge 86 of the passageway inlet effectively acts asa lower upper edge of the exhaust port 40b and cooperates with the sideedges 88 to reduce the effective area of the exhaust port 40b at anincreasing rate as the barrel section 80 is rotated from the high portposition toward the low port position. Such an arrangement isadvantageous for some applications because the smaller effective area ofthe exhaust port opening at low exhaust port conditions prevents overscavenging of the combustion chamber and improves fuel economy.

In the alternate construction illustrated in FIG. 11, a valvingarrangement similar to that illustrated in FIGS. 3-6 is employed forcontrolling the timing of the transfer port opening. More specifically,the barrel section 73a extends transversely of the transfer passage 30aand is mounted in the engine block 15 adjacent the upper edge 34a of thetransfer port 32a for rotational movement between a first or high portposition (illustrated by solid lines in FIG. 110 and a low port position(illustrated by dashed lines in FIG. 11). When the barrel section 73a isin the high port position, the notch 74a is situated with respect to thetransfer port 32a such that the notch edge 76a does not substantiallyaffect the effective distance of the upper edge 34a of the transfer port32a from the cylinder head end. When the barrel section 73a is in thelow port position, a portion of the barrel section extends past theupper edge 34a of the transfer port 32a and the notch edge 76aeffectively acts as a lower upper edge of the transfer port 32.

In construction illustrated in FIG. 12, a valving arrangement similar tothat illustrated in FIGS. 7-10 is employed for controlling the timing ofthe opening of a piston-controlled intake port. More specifically, thecrankcase 22`a is provided with an intake port 100 having upper andlower edges 102 and 104. Fuel-air mixture flows through an intakepassage 106 from a carburetor or the like and is introduced into thecrankcase 22a in response to a low pressure condition therein as thelower edge 26 of the piston 24 uncovers the lower edge 104 of the intakeport 100 during travel toward top dead center. The rotary barrel section80a of the valve member extends transversely of the intake passage 106and the passageway 82a is in registry with the intake passage 106 andthe intake port 100.

When the barrel section 80a is in the first or low port position(illustrated by solid lines in FIG. 12), the passageway 82a is situatedwith respect to the intake port 100 such that the passageway 82a and itsinlet have substantially no effect on the effective distance of thelower edge 104 of the intake port 100 from the cylinder head end. Whenthe barrel section 80a is in a second or high part position (illustratedby dashed lines in FIG. 12), the passageway inlet is situated withrespect to the intake port 100 so as to effectively reduce the distanceof the lower edge 104 of the intake port 100 from the cylinder head endand the effective area of the intake port opening is reduced asdescribed above in connection with the construction illustrated in FIGS.7-10. When early opening of the intake port 100 is desired for higherengine speed power, the barrel section 80a is rotated toward the lowport position. When later opening of the intake port 102 is desired forlower engine speeds, the barrel section 80a is rotated toward the highport position.

While the various valving arrangements have been described in connectionwith one engine port and for controlling the effective distance of oneedge of that port, it should be understood that each valving arrangementcan be used with any of the ports and arranged to vary the distance ofeither the upper edge or lower edge of the port from the cylinder headend.

Various of the features of the invention are set forth in the followingclaims:

I claim:
 1. A two-cycle internal combustion engine comprising an engineblock including a cylindrical wall defining a cylinder having a headend, a piston mounted for reciprocative movement in said cylinderrelative to said cylinder head end, a passage in said engine blockterminating at said cylindrical wall in a port having upper and loweredges at given distances from said cylinder head end and valve meansmounted for movement inside said passage relative to said port toselectively vary the effective distance of one of said port edges fromsaid cylinder head end, said valve means comprising a valve memberincluding an inner end portion having an arcuate edge portion which hasa concave contour corresponding to that of said cylinder wall and whichis chamfered, said valve member being mounted for radially reciprocativemovement relative to said cylindrical wall and to said port between afirst position wherein said valve member edge portion is spaced radiallyoutwardly from said wall and does not substantially affect the effectivedistance of said one port edge from said cylinder head end and a secondposition wherein said valve member edge portion is located adjacent saidwall and said port and acts as said one port edge to effectively changethe distance thereof from said cylinder head end, and means for movingsaid valve member between the first and second positions.
 2. A two-cycleinternal combustion engine according to claim 1 wherein said means formoving said valve means operates in response to variations in a variableengine operating parameter.
 3. A two-cycle internal combustion engineaccording to claim 1 wherein said passage comprises an exhaust passagethrough which exhaust gases are exhausted from said cylinder, whereinsaid port comprises an exhaust port having an upper edge located at apredetermined minimum distance from said cylinder head end, and whereinsaid valve member is located relative to said exhaust port such that,when said valve member is in the second position, said valve member edgeportion effectively acts as and lowers the upper edge of said exhaustport to a maximum predetermined distance from said cylinder head end.